Nitrogen fixation is a chemical process by which molecular nitrogen (N
2), which has a strong triple covalent bond, is converted into ammonia (NH
3) or related nitrogenous compounds, typically in soil or aquatic systems but also in industry. The nitrogen in air is molecular dinitrogen, a relatively nonreactive molecule that is metabolically useless to all but a few microorganisms. Biological nitrogen fixation or diazotrophy is an important microbe-mediated process that converts dinitrogen (N2) gas to ammonia (NH3) using the nitrogenase protein complex (Nif).
Cyanobacteria, also called Cyanobacteriota or Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name cyanobacteria refers to their color, which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not usually scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria.
Lysis is the breaking down of the membrane of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a lysate. In molecular biology, biochemistry, and cell biology laboratories, cell cultures may be subjected to lysis in the process of purifying their components, as in protein purification, DNA extraction, RNA extraction, or in purifying organelles.
Gunnera is the sole genus of herbaceous flowering plants in the family Gunneraceae, which contains 63 species. Some species in this genus, namely those in the subgenus Panke, have extremely large leaves. Species in the genus are variously native to Latin America, Australia, New Zealand, Papuasia, Hawaii, insular Southeast Asia, Africa, and Madagascar. The stalks of some species are edible.
Protein purification is a series of processes intended to isolate one or a few proteins from a complex mixture, usually cells, tissues or whole organisms. Protein purification is vital for the specification of the function, structure and interactions of the protein of interest. The purification process may separate the protein and non-protein parts of the mixture, and finally separate the desired protein from all other proteins. Ideally, to study a protein of interest, it must be separated from other components of the cell so that contaminants won't interfere in the examination of the protein of interest's structure and function. Separation of one protein from all others is typically the most laborious aspect of protein purification. Separation steps usually exploit differences in protein size, physico-chemical properties, binding affinity and biological activity. The pure result may be termed protein isolate.
Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as Nostoc punctiforme, Cylindrospermum stagnale, and Anabaena sphaerica. They fix nitrogen from dinitrogen (N2) in the air using the enzyme nitrogenase, in order to provide the cells in the filament with nitrogen for biosynthesis.
Protein splicing is an intramolecular reaction of a particular protein in which an internal protein segment is removed from a precursor protein with a ligation of C-terminal and N-terminal external proteins on both sides. The splicing junction of the precursor protein is mainly a cysteine or a serine, which are amino acids containing a nucleophilic side chain. The protein splicing reactions which are known now do not require exogenous cofactors or energy sources such as adenosine triphosphate (ATP) or guanosine triphosphate (GTP). Normally, splicing is associated only with pre-mRNA splicing. This precursor protein contains three segments—an N-extein followed by the intein followed by a C-extein. After splicing has taken place, the resulting protein contains the N-extein linked to the C-extein; this splicing product is also termed an extein.
Nostoc, also known as star jelly, troll’s butter, spit of moon, fallen star, witch's butter, and witch’s jelly, is the most common genus of cyanobacteria found in a variety of both aquatic and terrestrial environments that may form colonies composed of filaments of moniliform cells in a gelatinous sheath of polysaccharides. It may also grow symbiotically within the tissues of plants, providing nitrogen to its host through the action of terminally differentiated cells known as heterocysts. Nostoc is a genus that includes many species that are diverse in morphology, habitat distribution, and ecological function. Nostoc can be found in soil, on moist rocks, at the bottom of lakes and springs, and rarely in marine habitats. It may also be found in terrestrial temperate, desert, tropical, or polar environments.
Protein tags are peptide sequences genetically grafted onto a recombinant protein. Tags are attached to proteins for various purposes. They can be added to either end of the target protein, so they are either C-terminus or N-terminus specific or are both C-terminus and N-terminus specific. Some tags are also inserted at sites within the protein of interest; they are known as internal tags.
Glomeromycota are one of eight currently recognized divisions within the kingdom Fungi, with approximately 230 described species. Members of the Glomeromycota form arbuscular mycorrhizas (AMs) with the thalli of bryophytes and the roots of vascular land plants. Not all species have been shown to form AMs, and one, Geosiphon pyriformis, is known not to do so. Instead, it forms an endocytobiotic association with Nostoc cyanobacteria. The majority of evidence shows that the Glomeromycota are dependent on land plants for carbon and energy, but there is recent circumstantial evidence that some species may be able to lead an independent existence. The arbuscular mycorrhizal species are terrestrial and widely distributed in soils worldwide where they form symbioses with the roots of the majority of plant species (>80%). They can also be found in wetlands, including salt-marshes, and associated with epiphytic plants.
Flavodoxins (Fld) are small, soluble electron-transfer proteins. Flavodoxins contains flavin mononucleotide as prosthetic group. The structure of flavodoxin is characterized by a five-stranded parallel beta sheet, surrounded by five alpha helices. They have been isolated from prokaryotes, cyanobacteria, and some eukaryotic algae.
Cyanophages are viruses that infect cyanobacteria, also known as Cyanophyta or blue-green algae. Cyanobacteria are a phylum of bacteria that obtain their energy through the process of photosynthesis. Although cyanobacteria metabolize photoautotrophically like eukaryotic plants, they have prokaryotic cell structure. Cyanophages can be found in both freshwater and marine environments. Marine and freshwater cyanophages have icosahedral heads, which contain double-stranded DNA, attached to a tail by connector proteins. The size of the head and tail vary among species of cyanophages. Cyanophages infect a wide range of cyanobacteria and are key regulators of the cyanobacterial populations in aquatic environments, and may aid in the prevention of cyanobacterial blooms in freshwater and marine ecosystems. These blooms can pose a danger to humans and other animals, particularly in eutrophic freshwater lakes. Infection by these viruses is highly prevalent in cells belonging to Synechococcus spp. in marine environments, where up to 5% of cells belonging to marine cyanobacterial cells have been reported to contain mature phage particles.
Geosiphon is a genus of fungus in the family Geosiphonaceae. The genus is monotypic, containing the single species Geosiphon pyriformis, first described by Kützing in 1849 as Botrydium pyriforme. In 1915, Von Wettstein characterized Geosiphon pyriforme as a multinucleate alga containing endosymbiotic cyanobacteria, although he also noted the presence of chitin, a component of fungal cell walls. In 1933, Knapp was the first to suggest the fungal origin of the species and described it as a lichen with endosymbiotic cyanobacteria. It is the only member of the Glomeromycota known to not form a symbiosis with terrestrial plants in the form of arbuscular mycorrhiza.
Nodularins are potent toxins produced by the cyanobacterium Nodularia spumigena, among others. This aquatic, photosynthetic cyanobacterium forms visible colonies that present as algal blooms in brackish water bodies throughout the world. The late summer blooms of Nodularia spumigena are among the largest cyanobacterial mass occurrences in the world. Cyanobacteria are composed of many toxic substances, most notably of microcystins and nodularins: the two are not easily differentiated. A significant homology of structure and function exists between the two, and microcystins have been studied in greater detail. Because of this, facts from microcystins are often extended to nodularins.
Cyanobionts are cyanobacteria that live in symbiosis with a wide range of organisms such as terrestrial or aquatic plants; as well as, algal and fungal species. They can reside within extracellular or intracellular structures of the host. In order for a cyanobacterium to successfully form a symbiotic relationship, it must be able to exchange signals with the host, overcome defense mounted by the host, be capable of hormogonia formation, chemotaxis, heterocyst formation, as well as possess adequate resilience to reside in host tissue which may present extreme conditions, such as low oxygen levels, and/or acidic mucilage. The most well-known plant-associated cyanobionts belong to the genus Nostoc. With the ability to differentiate into several cell types that have various functions, members of the genus Nostoc have the morphological plasticity, flexibility and adaptability to adjust to a wide range of environmental conditions, contributing to its high capacity to form symbiotic relationships with other organisms. Several cyanobionts involved with fungi and marine organisms also belong to the genera Richelia, Calothrix, Synechocystis, Aphanocapsa and Anabaena, as well as the species Oscillatoria spongeliae. Although there are many documented symbioses between cyanobacteria and marine organisms, little is known about the nature of many of these symbioses. The possibility of discovering more novel symbiotic relationships is apparent from preliminary microscopic observations.
The Streptavidin-Binding Peptide (SBP)-Tag is a 38-amino acid sequence that may be engineered into recombinant proteins. Recombinant proteins containing the SBP-Tag bind to streptavidin and this property may be utilized in specific purification, detection or immobilization strategies.
Pentapeptide repeats are a family of sequence motifs found in multiple tandem copies in protein molecules. Pentapeptide repeat proteins are found in all species, but they are found in many copies in cyanobacterial genomes. The repeats were first identified by Black and colleagues in the hglK protein. The later Bateman et al. showed that a large family of related pentapeptide repeat proteins existed. The function of these repeats is uncertain in most proteins. However, in the MfpA protein a DNA gyrase inhibitor it has been suggested that the pentapeptide repeat structure mimics the structure of DNA. The repeats form a regular right handed four sided beta helix structure known as the Rfr-fold.
Crocosphaera watsonii is an isolate of a species of unicellular, diazotrophic marine cyanobacteria which represent less than 0.1% of the marine microbial population. They thrive in offshore, open-ocean oligotrophic regions where the waters are warmer than 24 degrees Celsius. Crocosphaera watsonii cell density can exceed 1,000 cells per milliliter within the euphotic zone; however, their growth may be limited by the concentration of phosphorus. Crocosphaera watsonii are able to contribute to the oceanic carbon and nitrogen budgets in tropical oceans due to their size, abundance, and rapid growth rate. Crocosphaera watsonii are unicellular nitrogen fixers that fix atmospheric nitrogen to ammonia during the night and contribute to new nitrogen in the oceans. They are a major source of nitrogen to open-ocean systems. Nitrogen fixation is important in the oceans as it not only allows phytoplankton to continue growing when nitrogen and ammonium are in very low supply but it also replenishes other forms of nitrogen, thus fertilizing the ocean and allowing more phytoplankton growth.
Cyanobacterial morphology refers to the form or shape of cyanobacteria. Cyanobacteria are a large and diverse phylum of bacteria defined by their unique combination of pigments and their ability to perform oxygenic photosynthesis.
David W. Wood is an American chemical engineer who is Professor of Chemical and Biomolecular Engineering at Ohio State University. Wood is also associated with the Department of Chemistry and Biochemistry and Molecular Biophysics Training Program.
